Direct air motor driven pump to dispense valve

ABSTRACT

A hot melt system includes a melt system, a feed system, and a dispensing system. Unlike traditional hot melt systems, the melt system is directly connected to a motor-driven pump of the dispensing system, without an intervening accumulation device.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Application No.61/556,541, filed on Nov. 7, 2011, and entitled “Direct Air Motor DrivenPump to Dispense Valve,” the disclosure of which is incorporated byreference in its entirety.

BACKGROUND

The present disclosure relates generally to systems for dispensing hotmelt adhesive. More particularly, the present disclosure relates to ahot melt pump with sufficiently uniform dispensing rates and fewercomponents.

Hot melt dispensing systems are typically used in manufacturing assemblylines to automatically dispense an adhesive used in the construction ofpackaging materials such as boxes, cartons and the like. Hot meltdispensing systems conventionally comprise a material tank, heatingelements, a pump and a dispenser. Solid polymer pellets are melted inthe tank using a heating element before being supplied to the dispenserby the pump. Because the melted pellets will re-solidify into solid formif permitted to cool, the melted pellets must be maintained attemperature from the tank to the dispenser. This typically requiresplacement of heating elements in the tank, the pump and the dispenser,as well as heating any tubing or hoses that connect those components.Furthermore, conventional hot melt dispensing systems typically utilizetanks having large volumes so that extended periods of dispensing canoccur after the pellets contained therein are melted. However, the largevolume of pellets within the tank requires a lengthy period of time tocompletely melt, which increases start-up times for the system. Forexample, a typical tank includes a plurality of heating elements liningthe walls of a rectangular, gravity-fed tank such that melted pelletsalong the walls prevents the heating elements from efficiently meltingpellets in the center of the container. The extended time required tomelt the pellets in these tanks increases the likelihood of “charring”or darkening of the adhesive due to prolonged heat exposure.

SUMMARY

A hot melt system includes a melt system, a feed system, and adispensing system. The feed system transports hot melt pellets to themelt system. The melt system heats hot melt pellets into a liquid, whichis then dispensed. The dispensing system includes a motor, a pump, and adispenser. The pump is driven by the motor, and the dispenser isdirectly connected to the outlet of the pump.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a system for dispensing hot melt adhesive.

FIG. 2 is a partial perspective view of a system for dispensing hot meltadhesive with a pump directly connected to a manifold.

FIG. 3 is a schematic view of a system for dispensing hot melt adhesive,the system having three dispense points.

DETAILED DESCRIPTION

FIG. 1 is a schematic view of system 10, which is a system fordispensing hot melt adhesive. System 10 includes cold section 12, hotsection 14, air source 16, air control valve 17, and controller 18. Inthe embodiment shown in FIG. 1, cold section 12 includes container 20and feed assembly 22, which includes vacuum assembly 24, feed hose 26,and inlet 28. In the embodiment shown in FIG. 1, hot section 14 includesmelt system 30, pump 32, and dispenser 34. Air source 16 is a source ofcompressed air supplied to components of system 10 in both cold section12 and hot section 14. Air control valve 17 is connected to air source16 via air hose 35A, and selectively controls air flow from air source16 through air hose 35B to vacuum assembly 24 and through air hose 35Cto motor 36 of pump 32. Air hose 35D connects air source 16 to dispenser34, bypassing air control valve 17. Controller 18 is connected incommunication with various components of system 10, such as air controlvalve 17, melt system 30, pump 32, and/or dispenser 34, for controllingoperation of system 10.

Components of cold section 12 can be operated at room temperature,without being heated. Container 20 can be a hopper for containing aquantity of solid adhesive pellets for use by system 10. Suitableadhesives can include, for example, a thermoplastic polymer glue such asethylene vinyl acetate (EVA) or metallocene. Feed assembly 22 connectscontainer 20 to hot section 14 for delivering the solid adhesive pelletsfrom container 20 to hot section 14. Feed assembly 22 includes vacuumassembly 24 and feed hose 26. Vacuum assembly 24 is positioned incontainer 20. Compressed air from air source 16 and air control valve 17is delivered to vacuum assembly 24 to create a vacuum, inducing flow ofsolid adhesive pellets into inlet 28 of vacuum assembly 24 and thenthrough feed hose 26 to hot section 14. Feed hose 26 is a tube or otherpassage sized with a diameter substantially larger than that of thesolid adhesive pellets to allow the solid adhesive pellets to flowfreely through feed hose 26. Feed hose 26 connects vacuum assembly 24 tohot section 14.

Solid adhesive pellets are delivered from feed hose 26 to melt system30. Melt system 30 can include a container (not shown) and resistiveheating elements (not shown) for melting the solid adhesive pellets toform a hot melt adhesive in liquid form. Melt system 30 can be sized tohave a relatively small adhesive volume, for example about 0.5 liters,and configured to melt solid adhesive pellets in a relatively shortperiod of time. Pump 32 is driven by motor 36 to pump hot melt adhesivefrom melt system 30, through supply hose 38, and deliver it to dispenser34. Motor 36 can be an air motor driven by compressed air from airsource 16 and air control valve 17. Pump 32 can be a linear displacementpump driven by motor 36. In the illustrated embodiment, dispenser 34includes manifold 40 and dispensing module 42. Hot melt adhesive frompump 32 is received in manifold 40 and dispensed via dispensing module42. Dispenser 34 can selectively discharge hot melt adhesive whereby thehot melt adhesive is sprayed out outlet 44 of dispensing module 42 ontoan object, such as a package, a case, or another object benefiting fromhot melt adhesive dispensed by system 10. Dispensing module 42 can beone of multiple dispensing modules that are part of dispenser 34. In analternative embodiment, dispenser 34 can have a different configuration,such as a handheld gun-type dispenser. Some or all of the components inhot section 14, including melt system 30, supply hose 38, pump 32, anddispenser 34, can be heated to keep the hot melt adhesive in a liquidstate throughout hot section 14 during the dispensing process.

System 10 can be part of an industrial process, for example, forpackaging and sealing cardboard packages and/or cases of packages. Inalternative embodiments, system 10 can be modified as necessary for aparticular industrial process application. For example, in oneembodiment (not shown), pump 32 can be separated from dispenser 34 andinstead attached to melt system 30. Supply hose 38 can then connect pump32 to dispenser 34.

FIG. 2 is a partial perspective view of system 10, showing pump 32 (withpump inlet 48 and pump outlet 50), dispenser 34, and motor 36. Dispenser34 includes manifold 40 and dispensing module 42. In the embodimentshown in FIG. 2, motor 36 is an air motor, which drives shaft 52 in areciprocating motion to drive a linear piston pump comprising pump 32.For example, NXT® air motors and MERKUR® pumps that are commerciallyavailable from Graco Inc. may be used as motor 36 and pump 32,respectively. Pump 32 has a changeover time, which is the amount of timethat the pump takes to reverse direction.

As shaft 52 is changing directions, pump 32 has a slower speed ascompared to when shaft 52 is moving between its extreme positions. Theamount of time pump 32 takes to change directions is preferably lessthan 250 milliseconds, more preferably less than 150 milliseconds, andeven more preferably less than 100 milliseconds.

Shaft 52 connects air motor 36 to pump 32. Pump inlet 48 is connected tomelt system 30 (FIG. 1). Dispenser 34 is directly connected to pump 32at pump outlet 50 via pipe 54, without an intervening accumulation hoseor other device or structure that provides accumulation. Directlycoupled indicates that a fluid passage of fixed or constant volume (e.g.non-expandable) is positioned between pump outlet 50 and dispenser 34.Pipe 54 is rigid, such as from being fabricated from steel or aluminum,so as to resist flexing. In other embodiments, a housing for pump 32 anda housing for manifold 40 can be fabricated from the same material, asan integral or monolithic component. In those embodiments, pipe 54 maybe a hole cut through the integral or monolithic component. Thus, asmotor 36 runs, pump 32 will take in liquefied adhesive at pump inlet 48.The liquefied adhesive is pumped directly to dispenser 34 via pipe 48and pump outlet 50, and through manifold 40 to dispensing module 42,where it is dispensed through outlet 44. The embodiment shown in FIG. 2does not include an accumulation hose between pump 32 and dispenser 34.By utilizing a pump with low changeover time, the accumulation hose isno longer necessary to provide suitable uniformity of dispensing ratesfor many applications.

By using a pump with short changeover time, variability in the outputrate of a hotmelt adhesive dispensing system is minimized. Pumps withlonger changeover times create pressure profiles that are not constantwith respect to time, which results in shot sizes from dispensing module42 having different volumes. To alleviate this drawback, conventionalhot melt systems often incorporate a tube of an elastic material toprovide an “accumulation” effect, storing energy during pressure peaksand releasing it during periods of low pressure. However, not allapplications require precise shot sizes. Furthermore, elastic hoses needto be heated and maintained, which adds to cost to the operation of thesystem. In one embodiment of the invention, a dispenser has noaccumulator, and the manifold is directly connected to the pump.

FIG. 3 is a schematic diagram of a portion of system 10. FIG. 3 showspump 32, dispenser 34, and motor 36. As described in FIG. 2, pump 32 isconnected to both dispenser 34 and motor 36. There is no accumulationhose between pump 32 and manifold 40 of dispenser 34. Dispenser 34includes manifold 40, dispensing modules 42, and outlets 44. In theembodiment shown in FIG. 3, there are three dispensing modules 42. Onedispensing module 42 is attached directly to manifold 40, as shown inFIG. 2. Additionally, two dispensing modules 42 are connected tomanifold 40 by hoses 46.

Most hoses will have some accumulation effect due to elasticity of thematerial that makes up the hose. For example, hoses 46 may be made of anelastomer such as vulcanized rubber, or a metal, each of which has someelasticity. The invention includes those embodiments of system 10 whichhave hoses capable of accumulation effect downstream of manifold 40. InFIG. 3, there is no accumulation hose between pump 32 and manifold 40,and none between manifold 40 and one of dispensing modules 42. FIG. 3shows that multiple dispensers 34 may be included within system 10.Dispensers 34 may be connected to manifold 40 either directly or throughan intermediate structure, such as hoses 46.

While the invention has been described with reference to an exemplaryembodiment(s), it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment(s) disclosed, but that theinvention will include all embodiments falling within the scope of theappended claims.

1. A hot melt system comprising: a melt system capable of heating hotmelt pellets into a liquid; a feed system for transporting hot meltpellets to the melt system; and a dispensing system for administeringliquefied hot melt pellets from the melt system, the dispensing systemincluding: a motor; a pump driven by the motor; and a dispenser directlyconnected to the pump.
 2. The hot melt system of claim 1, furthercomprising a container for storing unmelted hot melt pellets, and fromwhich the feed system receives hot melt pellets.
 3. The hot melt systemof claim 1, wherein the pump has a changeover time of less than 250milliseconds.
 4. The hot melt system of claim 1, wherein the motor is anair motor.
 5. The hot melt system of claim 3, wherein the motor is adouble acting piston pump.
 6. The hot melt system of claim 1, whereinthe dispenser comprises a manifold and a dispensing module, thedispensing module having an outlet.
 7. The hot melt system of claim 6,wherein the pump has an outlet and the dispenser manifold has an inlet,and the outlet of the pump is directly connected to the inlet of thedispenser manifold.
 8. The hot melt system of claim 6, wherein themanifold has an outlet and the dispensing module has an inlet, and theoutlet of the manifold is directly connected to the inlet of thedispensing module.
 9. The hot melt system of claim 6, further comprisinga plurality of outlets from the dispenser manifold.
 10. The hot meltsystem of claim 1, wherein the dispenser is coupled to the pump via acoupling that defines a fixed flow path volume.
 11. A hot melt adhesivedispensing system, comprising: a motor; a pump having a changeover timeof less than 250 milliseconds of operating time, wherein the pump isdriven by the motor, for pumping a liquid hot melt adhesive; and adispenser, directly connected to the pump, for dispensing the liquid hotmelt adhesive.
 12. The dispensing system of claim 11, wherein the motoris an air motor.
 13. The dispensing system of claim 11, wherein there isno accumulation device between the pump and the dispense valve.
 14. Thedispensing system of claim 11, wherein the pump is a double-actingpiston pump.
 15. A method of dispensing hot melt adhesive, the methodcomprising: melting pellets of adhesive in a melt system to form aliquid adhesive; pumping the liquid adhesive to a dispenser manifoldthat is directly connected to a pump outlet; and dispensing the liquidadhesive from the dispenser manifold through a module.
 16. The method ofclaim 15, further comprising supplying the pellets of unmelted adhesivefrom a container to the melt system.
 17. The method of claim 15, whereinpumping the liquid adhesive to the dispenser manifold includes using apump.
 18. The method of claim 17, wherein the pump is a double-actingpiston pump.
 19. The method of claim 15, wherein dispensing the liquidadhesive further includes selectively dispensing liquid adhesive fromany of a plurality of valves connected to the dispenser manifold. 20.The method of claim 15, further comprising passing the liquid adhesivefrom the pump outlet to the manifold through a fixed-volume flow path.